This invention relates to a manually operated control mechanism and is particularly directed toward a device in which a first actuator may be used to position a control arm at a desired setting while a second actuator may temporarily reposition the control arm at a different setting without disturbing the setting achieved by the first actuator. Upon release of the second actuator the control arm is returned to the setting attained by the first actuator.
The invention is particularly applicable to various devices where a manually actuated lever is employed to adjust a mechanical linkage or the like at a predetermined position while retaining the capability to reposition the mechanical linkage temporarily. It is especially applicable to engine governors and it is shown and described herein as so used for purposes of illustration.
It is conventional practice to employ a governor to maintain a constant engine speed under varying load conditions particularly in heavy earth-moving equipment, where generally a compression type ignition engine is used. Various types of governors used in such applications are generally well-known in the art. A governor represented of the type herein considered is found in U.S. Pat. No. 2,961,229, assigned to the assignee of this invention. Generally, governors of the type herein described utilize a spring loaded device in a control lever to tension the governor spring. Particular tensioning of the governor spring determines the operating setting of the engine. In operation of heavy earth-working equipment it is desirable to position the governor setting at a particular engine speed to produce a particular operating speed over the ground while retaining the capability to slow the engine for brief periods without disturbing the operating speed setting of the governor.
Various schemes have been utilized to accomplish such a constant setting, but in most cases the schemes have proven complicated and in some cases cumbersome. In the operation of heavy construction equipment it is extremely desirable to provide an operating scheme for the vehicle which allows the operator to devote his attention to the job at hand. Thus, simplicity of controls is of great importance. Use of the more complex governor control systems presently available may require diversion of operator attention from the task at hand. Use of hand controls to achieve governor control is appropriate in certain systems, however in other systems wherein hand control levers control an associated implement it would be appropriate to utilize a pedal or foot operated lever to decelerate the engine from the governor controlled operating setting. Previously designed governor and decelerator control linkages which utilize a dual lever arm arrangement including an extensible link interconnecting the hand operated control lever for setting the governor have suffered from the disability that the hand control lever can be positioned beyond the normal high idle setting of the governor. Although this positioning of the control lever does not affect the governor setting, per se, as the motion is lost in the extensible link; it does affect engine operation when the operator wishes to briefly decelerate the engine utilizing the second decelerator lever as the extensible link prevents the engine from reaching its lowest idle setting. Therefore, it would be appropriate to provide a governor and decelerator control linkage which prevents the aforedescribed false high idle position while accomplishing the advantages of a simple design requiring the least amount of operator attention.